The present invention relates generally to the field of modular plugs for terminating cables. More particularly, it relates to an improved plug for terminating communication cables having a plurality of twisted signal pairs of conductors and controlling the positions of the untwisted conductors in order to reduce near-end crosstalk.
Communications networks generally transmit data at a high frequency over cables having a plurality of twisted signal pairs of conductors. For example, according to currently accepted performance standards, Category 5 products operate at frequencies up to 100 MHz and Category 6 products operate at frequencies up to 250 MHz over Unshielded Twisted Pair (UTP) cable that contains eight (8) individual conductors arranged as four (4) twist pairs. When data is transmitted via an alternating current in a typical telecommunication application at such high frequencies, each individual conductor and each signal pair creates an electromagnetic field that can interfere with signals on adjacent conductors and adjacent signal pairs. This undesirable coupling of electromagnetic energy between adjacent conductor pairs, referred to as crosstalk, causes many communications problems in networks.
Crosstalk is effectively controlled within communication cables through the use of twisted pairs of conductors. Twisting a signal pair of conductors causes the electromagnetic fields around the wires to cancel out, leaving virtually no external field to transmit signals to nearby cable pairs. In contrast, Near End Crosstalk (NEXT), the crosstalk that occurs when connectors are attached to twisted pair cables, is much more difficult to control. Since twisted signal pairs must be untwisted into individual conductors in order to attach a connector, high levels of NEXT are introduced when portions of transmitted signals within the connector are electromagnetically coupled back into received signals.
In efforts to control NEXT, a wide variety of modular plugs have been developed for terminating communications cables that contain twisted signal pairs of conductors. As communication technology advances, however, and allows transmission at higher and higher frequencies, the modular plugs known in the prior art are no longer capable of maintaining NEXT levels within the ranges specified in widely accepted national performance standards. For Category 6 products, for example, the Commercial Building Telecommunications Wiring Standard (ANSI/TIA/EIA-568) specifies a de-embedded NEXT test plug range which all patch cord plugs should meet to ensure interoperable Cat 6 performance. In order to satisfy TIA/EIA 568B-2.1, patch cord plugs must be designed with low NEXT variability centered within the specified de-embedded NEXT test plug range. In standard plug designs, however, pair-to-pair distortion, twist rate, and individual conductor positions are not strictly controlled. Hence, large variations of NEXT performance occur. Prior art modular plug designs also cause increased de-embedded NEXT variability by utilizing strain relief components that consist of a latching bar that pinches the cable jacket, prohibiting cable movement within the plug housing. In order to generate sufficient retention force, these bar style strain relief components significantly deform the cable jacket and the twisted pair conductors within the jacket. This pinching deformation causes distortion and displacement of twisted pairs of conductors that in turn causes increased de-embedded NEXT variability.
Accordingly, there is a demand for an improved modular cable termination plug.
The present invention overcomes the deficiencies of the prior art by providing an improved modular cable termination plug. The improved modular cable termination plug of the claimed invention utilizes mechanical features that will control the twist rate, un-twisted length, and position of individual conductors as well as twisted pairs of conductors within a cable and ensure repeatable placement of the conductors from the undisturbed cable to the point of termination. Accordingly, in comparison to the modular cable termination plugs available in the prior art, the claimed invention is more versatile and provides reduced NEXT variability and enhanced performance.
In accordance with the present invention, the improved modular cable termination plug comprises a conductor divider having an entrant barb and a plurality of conductor divider channels, a load bar having a plurality of through holes, and a plurality of contact terminals of alternating heights. In one embodiment of the invention, the conductor divider and the load bar hold conductors in three separate horizontal planes in order to minimize crosstalk between adjacent signal pairs of conductors. One embodiment of the present invention also provides for a housing and a plurality of slots in the load bar that are adapted to receive the plurality of contact terminals. The integral slots in the load bar provide an advantage over the prior art by reducing the overall length of untwisted cable within a housing.
It is another feature of the invention to provide a cable strain relief. In one embodiment, a strain relief collar secures the load bar, conductor divider, and cable within a housing. In another embodiment of the claimed invention, a strain relief boot protects the bend radius of the cable.
It is yet another feature of the invention to provide a method of separating and arranging signal pairs of conductors in order to minimize the crosstalk within a modular connector plug. According to the method, untwisted signal pairs are separated and arranged into three separate planes, and individual conductors are separated and arranged in three separate planes and are terminated by contact terminals having varying heights.
These and other features and advantages of the present invention will be apparent to those skilled in the art upon review of the following detailed description of the drawings and preferred embodiments.